// Copyright (C) 2024 Kumo inc.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//

#pragma once

#include <cstddef>
#include <type_traits>

namespace merak {

template <typename B, typename E, typename S>
constexpr std::enable_if_t<std::is_integral<std::decay_t<B>>::value && 
                           std::is_integral<std::decay_t<E>>::value && 
                           std::is_integral<std::decay_t<S>>::value, bool>
is_range_invalid(B beg, E end, S step) {
  return ((step == 0 && beg != end) ||
          (beg < end && step <=  0) ||  // positive range
          (beg > end && step >=  0));   // negative range
}

template <typename B, typename E, typename S>
constexpr std::enable_if_t<std::is_integral<std::decay_t<B>>::value && 
                           std::is_integral<std::decay_t<E>>::value && 
                           std::is_integral<std::decay_t<S>>::value, size_t>
distance(B beg, E end, S step) {
  return (end - beg + step + (step > 0 ? -1 : 1)) / step;
}

}  // end of namespace merak -----------------------------------------------------
